Department of Physics and Astronomy, West Virginia University
Fe-based superconductors share a common building block of a square lattice of Fe ions tetrahedrally coordinated to Pn or Ch ions, where the Tc is controlled by the local geometry of the FePn(Ch)4 tetrahedron. The optimal Tc is achieved when the bond angle of Pn(Ch)–Fe–Pn(Ch) is tuned to that of a normal tetrahedron (109.5°). In this talk, I will present our work on epitaxial single-layer Fe-chalcogenide films on the SrTiO3 substrate where we modify the Ch-Fe-Ch angle via UV light, chemical pressure, and substrate termination. From comprehensive studies using in-situ STM/ARPES, ex-situ TEM imaging and x-ray scattering, and DFT/DMFT calculations, we've discovered a strong correlation between the Tc and the Ch-Fe-Ch angle in these single-layer films. I will also highlight our findings on topological edge states in multilayer films and the evidence of Tomonaga-Luttinger liquid behavior and its tunability by chemical pressure. These findings shed light on the topological properties and pairing symmetry in Fe-chalcogenide superconductors.
Brief CV of Prof. Lian Li:
Lian Li is currently the Robert L. Carroll Professor of Physics at the Dept. of Physics and Astronomy, West Virginia University. He received his Ph.D. from Arizona State University in 1995. He received the E. W. Müller Outstanding Young Scientist Award from the International Field Emission Society (1996) and NSF CAREER Award (2001). He is interested in MBE growth of quantum materials (e.g., Fe-chalcogenides, topological insulators, and Kagome magnets) and characterization using in-situ low-T STM/S and ARPES.
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